CRYSTAL-STRUCTURE, MAGNETIC-PROPERTIES, X-RAY-PHOTOEMISSION-SPECTROSCOPY, AND SPECIFIC-HEAT MEASUREMENTS ON PR2BAO4 AND PRBAO3

We investigated Pr2BaO4 and PrBaO3 by several complementary experimental techniques. PrBaO3 crystallize in an orthorhombic structure. dc and ac susceptibility measurements exhibit irreversibility phenomena below T(N) = 11.7 K and reveal the magnetic structure of PrBaO3, which consists of an anti-ferromagnetic ordering together with a small canting of the spins which produces the ferromagnetic component. Both magnetic and specific-heat studies show that T(N) is not affected by the applied magnetic field up to 9 T. Pr2BaO4 crystallizes in an orthorhombic structure where a=10.56 angstrom, b=12.43 angstrom, and c=3.617 angstrom belongs to Pnam space group. dc and ac susceptibility and specific-heat measurements show that Pr2BaO4 is paramagnetic down to 2 K, with a vanishing electronic specific-heat coefficient gamma. X-ray photoemission spectroscopy shows that Pr is mainly trivalent in Pr2BaO4 and close to being tetravalent in PrBaO3. The pronounced ferromagnetic-like behavior found below 11.7 K in the PrxR1-xBa2Cu3Oz system is due to the impurity of PrBaO3.